I'm a "text/call when you get there" person. Usually this is in bad weather, at night, long distances, and if you're driving through the mountains. At first, it was really awful. I'd panic if someone drove period anywhere and I didn't get a call, then I worked past that and it was just if I didn't hear from them in one of the above instances, now it works more like this:

Jane is leaving my house and driving home, it's late and dark out, Jane lives about 20 minutes away. As she leaves I say goodnight and say "let us know you got home safe". After she left we clean up a bit, let the dogs out one last time and head to bed. Before we go to sleep I don't recieve a text from Jane, oh well I figure she's not home yet, maybe she stopped for something along the way. The next morning I awake and check my phone to see...still not text from Jane. Ok, now I start to worry a bit and send her a good morning text (not odd in my group of friends to text someone to randomly say good morning). If I get a response, all is good. I don't care she didn't text the minute she walked in. If I get no response, I start to worry a bit more. I might wait an hour or two and text again to make sure she's ok. I've never gone longer then a few hours without a "I'm fine just didn't see the text" response, so I'm not sure what my next move would be. But I'd be panicking a little more, probably some quick social media stalking (well she shared the cute Panda photo at 5am, so she was alive then).

For me, I've lost someone without ever getting an "I'm ok text" without ever asking for one or expecting one. With assuming "no news is good news". Having already gone through that (it was dark and they were driving in the mountains, so two of my qualifiers for a text/call), it's a constant thought in my head. Even without focusing on it, it's there. It's a reality I now know exists.

I kind of think of it as just making sure everyone is safe. I drive at night, long distances, through the mountains, in bad weather sometimes all at once. And nothing has happened. In fact I assume for the most part, nothing will happen. But there's the what if that lives in the back of my brain and slowly gets louder when I don't hear anything.

My parents live about two hours away from where DH and I live. I usually do call them just to say "Got home fine," if we've been visiting them, but not always. If the weather and/or the roads are bad for some reason, I definitely call. Partly because it makes Mom and Dad feel better, and I feel better knowing that someone has an idea of when they should start worrying. Granted, the road we're on is mostly pretty well travelled, but a good chunk of the trip is also through fairly rural areas, where things like hitting deer aren't uncommon.

When I was single and sharing an apartment with my best friend, she and I usually kept each other informed about our plans if we had separate plans. Not in great detail, but something like "I'm going to do X this weekend, should be back around Y time." That way, at least there was someone who had an idea of where/when to start looking if there was a problem. We considered it both a safety measure and a courtesy to the person we lived with.

I'm of the school of thought once someone says "I'm depressed" (and they mean it not I'm having a sad day/week. I'm talking about DEPRESSION not I've got the blues lately) you are allowed to do whatever you want with that info to get them help. I would have no qualms telling their spouse and or siblings